Effects of fuel change to electricity on PM2.5 local levels in the Bus Rapid Transit System of Bogota.

The TransMilenio (TM) is a transport system. Twenty-year-old TM is a fast, highly efficient, and self-sufficient mode of passenger transport. This work aims to evaluate the effects of changing current TM diesel buses by electricity-powered buses (battery, wire-based), on the PM concentrations at surface level. Emissions calculations considering combustions and resuspension of TM and Non-TM were performed. A CFD model was implemented to estimate current PM concentrations at the roadside level, and the CFD results were validated using the statistic parameters: MB, RMSE, r, and IOA. Results from the emission calculations indicate that TM buses (30-50%) are one of the main sources of primary PM in all the considered urban sites in this study. Non-exhaust emissions from most vehicle categories were also identified as an important source of primary PM (40% of total emissions). The CFD model reproduced closely the trends and levels of PM concentrations measured at the roadside level in all the locations. Replacing TM diesel vehicles with electric vehicles reduces PM concentrations between 10 and 30% according to the CFD results obtained. Higher reductions can be achieved if policies are adopted to control other types of vehicles and non-exhaust emissions since they have a contribution of about 60%. Finally, this study shows that the combined use of emission calculations and advanced near-road dispersion models are useful tools to study and manage air quality in large cities.